For coating materials for heat resistant insulated wires, medical parts, parts for chemicals storage tank of a semiconductor production device, and parts for carrier and piping, fluorine-containing copolymers such as a tetrafluoroethylene (hereinafter referred to as TFE)/perfluoro(alkyl vinyl ether)copolymer (hereinafter referred to as PFA), a TFE/hexafluoropropylene (hereinafter referred to as HFP) copolymer (hereinafter referred to as FEP) and a TFE/ethylene copolymer (hereinafter referred to as ETFE), and polytetrafluoroethylene (hereinafter referred to as PTFE), are used as molding materials, in view of excellent electrical insulating properties, low-dielectric constant, heat resistance and chemical resistance. It is possible to carry out melt-molding of molding materials consisting of a fluorine-containing copolymer such as PFA, FEP or ETFE, and such molding materials can be molded by means of various molding methods such as injection molding, extrusion and rotational molding.
However, with respect to molding materials consisting of such a fluorine-containing copolymer, molded products may slightly be yellowed during melt-molding in some cases, and the colored molded products may cause decrease in yield of manufactured articles, since strict product quality is required particularly for parts for medical application and semiconductor device application.